Pontes de Carvalho L C, Tomlinson S, Vandekerckhove F, Bienen E J, Clarkson A B, Jiang M S, Hart G W, Nussenzweig V
Department of Pathology, New York University Medical Center, New York 10016.
J Exp Med. 1993 Feb 1;177(2):465-74. doi: 10.1084/jem.177.2.465.
Here we report the presence of a trans-sialidase on the surface of Trypanosoma brucei culture-derived procyclic trypomastigotes. The enzyme is not detected in lysates of bloodstream trypomastigotes enriched for either stumpy or slender forms. The trans-sialidase catalyzes the transfer of alpha(2-3)-linked sialic acid residues to lactose. beta-galactopyranosyl residues are at least 100 times better acceptors for sialic acid than alpha-galactopyranosyl residues. In the absence of efficient acceptors, the purified enzyme transfers sialic acid to water, i.e., it acts as a sialidase. Although the T. cruzi and T. brucei trans-sialidases have very similar donor and acceptor specificities, they are antigenically distinct. Sodium dodecyl sulfate-polyacramide gel electrophoresis under nonreducing conditions and silver staining of the purified trans-sialidase reveals a single band of 63 kD. When the surface membrane of live procyclic trypomastigotes is trans-sialylated, using radioactive sialyllactose as the donor substrate, it appears that the only sialylated surface molecule is procyclin. Pronase treatment of live parasites removes only part of the surface sialic acid, in agreement with recent data showing that the glycosylphosphatidylinositol anchor of procyclin is sialylated (Ferguson, M. A. J., M. Murray, H. Rutherford, and M. J. McConville. 1993. Biochem. J. In press).
在此我们报告，在布氏锥虫培养来源的前循环型锥鞭毛体表面存在一种转唾液酸酶。在富含粗短型或细长型的血流型锥鞭毛体裂解物中未检测到该酶。转唾液酸酶催化α(2 - 3)连接的唾液酸残基转移至乳糖。β - 吡喃半乳糖基残基作为唾液酸受体的能力比α - 吡喃半乳糖基残基至少强100倍。在缺乏有效受体的情况下，纯化后的酶将唾液酸转移至水中，即它发挥唾液酸酶的作用。尽管克氏锥虫和布氏锥虫的转唾液酸酶具有非常相似的供体和受体特异性，但它们在抗原性上是不同的。在非还原条件下进行十二烷基硫酸钠 - 聚丙烯酰胺凝胶电泳并对纯化后的转唾液酸酶进行银染，显示出一条63 kD的单带。当使用放射性唾液酸乳糖作为供体底物对活的前循环型锥鞭毛体的表面膜进行转唾液酸化时，似乎唯一被唾液酸化的表面分子是前环素。用链霉蛋白酶处理活寄生虫仅去除部分表面唾液酸，这与最近的数据一致，该数据表明前环素的糖基磷脂酰肌醇锚被唾液酸化（弗格森，M. A. J.，M. 默里，H. 卢瑟福，和M. J. 麦康维尔。1993. 《生物化学杂志》待发表）。
